TITLE:
Evaluation and Validation of Recent Freely-Available ASTER-GDEM V.2, SRTM V.4.1 and the DEM Derived from Topographical Map over SW Grombalia (Test Area) in North East of Tunisia
AUTHORS:
Sarra Ouerghi, Ranya Fadlalla Abdalla ELsheikh, Hammadi Achour, Samir Bouazi
KEYWORDS:
Digital Elevation Models (DEMs), Reference DEM, ASTER-GDEM, SRTM, Comparisons, Morphometric Index
JOURNAL NAME:
Journal of Geographic Information System,
Vol.7 No.3,
June
2,
2015
ABSTRACT: Digital Elevation Models (DEMs)
provide one of the most useful digital datasets for a wide range of users. Both
the Shuttle Radar Topographic Mission (STRM V.4.1) topography and the Advanced
Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation
Model (ASTER-GDEM V.2) have been widely used in geomorphology, hydrology,
tectonic, and others since they were made access to the public. The magnitude
of vertical errors of two near-global DEMs—SRTM and ASTER-GDEM is compared and
validated against a reference DEM which has a relatively high precision of
1:25,000 scale constructed from topographical map. Moreover, the reference DEM,
ASTER-GDEM and SRTM were used as basic topographic data to extract some
Morphometric index. The parameters like slope and shaded reflectance maps, were
derived from the elevation distribution to provide a more sensitive indication
of DEM quality. A square area in the North East of Tunisia was selected as a
case study to test and evaluate the elevation accuracy of ASTER-GDEM and SRTM.
The relative accuracy approach and absolute accuracy were adopted to evaluate
global DEMs. The comparisons show that SRTM overestimates and ASTER-GDEM
underestimates elevations, both DEMs can be used to extract the elevations of
required geometric data,i.e.sub watershed boundaries,
drainage information and cross sections. However, small errors still exist in.
The lower root mean square errors values indicate that SRTM is comparatively
more accurate than ASTER-GDEM.